Samsung error codes starting with a 6 all relate to controls errors.

An E653, Temperature sensor open/short error relates the temperature sensor in the wired controller, not the indoor or outdoor units. The sensor in the wired controller is connected via a small plug. Checking the connection of the sensor to the controller PCB is recommended (especially in the event of this error occurring with a new controller), as the sensor plug may just be loose. The sensor resistance can be checked with a multi meter, it should read around 10 Kohm at 25 degrees. The sensor is available as a spare part.